Tuesday, September 09, 2008

As plug-in hybrid cars come closer to a reality, the EPA and the automakers are going to have to figure out how to deal with them. The EPA is required to set a fuel economy rating for each car on the road. And that's usually a straight forward testing procedure. Even if your results will vary, you still have a way of comparing vehicles for their fuel efficiency. But plug-in hybrids are going to be a different story.

Since plug-in hybrids run off electric power until the battery power runs down, for some amount of distance, the fuel economy is off the charts. Take the Volt (labeled an extended range electric vehicle, E-REV), for instance. After being fully charged by plugging in, the Chevy Volt is supposed to travel 40 miles on electric power alone.

After that, the gas engine will kick in, but not to move the vehicle. The small gas engine will only recharge the battery pack.

And according to Motortrend, that's causing a headache for the EPA and for GM. According to GM, you can get over 100 mpg using the Volt. The EPA, however wants the battery to be fully recharged by the gas engine before it takes its reading. That would set the fuel economy at 48 mpg.

Now, 48 mpg is nothing to laugh at. Most car companies (except for Toyota with the Prius) would love for a gas powered engine to get that sort of rating from the EPA. But GM is worried about what that sort of rating could do to those potential customers of the Volt.

But I would also like to think, no matter what the rating the EPA eventually gives, most people will still be interested no matter what the EPA says. A lot of people could drive less than 40 miles a day and never buy gas (Dumb question: Does just leaving the gas in the compartment lead to issues? I know you shouldn't leave a gas mower over the winter with a full tank of gas. Will the same issues affect those people who don't travel over 40 miles a day and are faithful about plugging it back in?) Others will still love to go 40 miles on electric power alone, but still be able to get to where they're going without having to worry about plugging in.

Besides which, isn't 48 mpg the rating you want to know about? You know you can go 40 miles on electric power. What you don't know is how far you can go after that. In the end, will the EPA have to come up with an electric range along with a fuel economy figure?

Either way, there's not a lot of time left for the EPA to figure this one out. Plug-ins are coming soon.

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